Ultra narrow channel ultra low refrigerant charge evaporative condenser

ABSTRACT

A tube bundle for an evaporative refrigerant condenser having a plurality of straight single pass tubes extending between a refrigerant inlet header and a refrigerant outlet header, said tubes having a cross-sectional shape in the form of an ellipse having a major axis and a minor axis, wherein said major axis is longer than said minor axis by a factor of 3 to 7, wherein the amount of required refrigerant charge for a particular heat exchange capacity is substantially and unexpectedly reduced resulting in a substantial and unexpected increase in efficiency.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to evaporative condensers and coolers.

Description of the Background

In certain cooling/refrigeration system, evaporative condensers receivesuperheated refrigerant gas from a cooling/refrigeration systemcompressor and cool/condense it to refrigerant liquid, which condensedrefrigerant liquid is then return to a cooling/refrigeration systemevaporator for cooling/refrigeration of a desired space. The evaporativecondensers include a series of round or slightly elliptical serpentinetubes through which the refrigerant passes. Water is flowed over thetubes containing the refrigerant, allowing heat to be transferred fromthe refrigerant to the water via indirect heat exchange and causing thesuperheated refrigerant gas to condense to liquid. The heated water inturn is cooled by direct heat exchange with ambient air as the water andambient air pass over the tubes and/or through fill material.

SUMMARY OF THE INVENTION

The present invention is a new design for evaporative refrigerantcondensers including an indirect refrigerant condensing tube bundle heatexchanger with single pass (no serpentine) extremely narrow ellipticaltubes (ratios of tube height to tube width of 3:1 to 16:1) to increasethe refrigerant velocity (void fraction). For example, for a nominaltube diameter 1″ round tube, the preferred tube width of the tubes ofthe invention is approximately 0.1 inches to 0.5 inches, outsidediameter, with tube height about 1.4 inches to 1.6 inches, outsidediameter (vertical axis of ellipse). Similarly, at the other end ofnominal tube diameter spectrum, for a nominal diameter ¼″ round tube,the preferred tube width of the tubes of the invention is approximately0.025 inches to 0.125 inches, outside diameter, with tube height about0.3 inches to 0.4 inches, outside diameter (vertical axis of ellipse).

Each single pass tube terminates at one end at an inlet refrigerantheader and at the other end at an outlet refrigerant header. The tubesmay be galvanized or stainless steel. The tubes may be provided with aflared inlet to reduce inlet refrigerant pressure loss. According to apreferred embodiment, tube spacing may be approximately 0.5 inches to0.75 inches, center to center. According to another embodiment, eachtube may be offset vertically relative to adjacent tubes to reduce airdP loss so that adjacent tubes nest into one-another.

This design reduces the cross sectional refrigerant flow areasignificantly, thus significantly reducing the required refrigerantcharge, while maintaining the external heat exchange surface and thusheat exchange capacity, resulting in an unexpected increase inefficiency of more than 20% relative to the same device with serpentineelliptical tubes.

According to a first embodiment of the invention, the refrigerantcondensing tube bundle of the invention may be substituted for theserpentine coil from a standard evaporative closed circuitcooler/condenser.

According to another embodiment of the invention, the refrigerantcondensing tube bundle described above may be combined with (placedinto) an otherwise standard counterflow direct evaporative cooling towerto create a new type of evaporative refrigerant condenser/cooling tower.According to various alternative embodiments, the tube bundle may beused as the structural support for fill, supporting various amounts offill height, for example, but not limited to, 6 inches, 1′, 1.5′, 2′,2.5′, 3′, 3.5′, 4′ or more of film fill height, or any amounts inbetween. According to these tube-bundle-as-fill-support embodiments, thebottom fill bundles should preferably be run perpendicular to thecondenser tubes for best water distributions on the tubes. Standardcooling tower nozzle arrangements may be used with water flow rates aslow as 2 gpm/sf, with preferable amounts of 4 gpm/sf to 10 gpm/sf, andmore preferably from around 5 gpm/sf to 7 gpm/sf.

According to some embodiments, the tubes in the tube bundle may have aslight slope from horizontal to allow for drainage of liquidrefrigerant.

According to various different embodiments of lengths of the tubes ofthe tube bundle may run either long or short way across the towerdepending on thermal and refrigerant load.

According to an alternative embodiment, the tube bundle of the inventionmay be used in a counterflow closed circuit cooler arrangement in whichthe fan, water distribution nozzles, heat and mass exchange fill and airinlets are all positioned above a water redistribution basin, which inturn is positioned above a closed circuit cooler coil of the invention.This embodiment produces a substantial reduction in height due to thelack of serpentine tube bends in the tube bundle of the invention. Thetube spacing of the present invention used in a counterflow closedcircuit cooler can be much tighter with less space between tubes, sinceonly water and no air needs to flow between tubes.

According to further alternative counterflow embodiments, the coilbundle of the invention may be located just above the fill and below thespray nozzles.

According to further embodiments, the tube bundle of the invention maybe used with various crossflow arrangements. According to one suchembodiment, the tube bundle is located above the crossflow fill andbelow the nozzle distribution system and air flows downward through thetubes before exiting to the fan plenum. According to another suchembodiment, the tube bundles of the invention may be located above,below and in the middle of the crossflow fill. According to thisembodiment, no air passes over the tubes, only water, as the cooledwater flows from one fill section down to the next.

A more detailed description of the invention is set forth below withreference to the following figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a tube according to an embodiment ofthe invention.

FIG. 2 is a cross-sectional view of a tube according to anotherembodiment of the invention.

FIG. 3 is a perspective view of a tube bundle according to an embodimentof the invention

FIG. 4 is a top/overhead view of the embodiment shown in FIG. 3.

FIG. 5 is a side view of the embodiment shown in FIGS. 3 and 4.

FIG. 6 is an end view of the embodiment shown in FIGS. 3-5.

FIG. 7A is a representation of a prior art closed circuitcooler/condenser with serpentine coil.

FIG. 7B is a representation of a closed circuit cooler/condenser with anultra-narrow elliptical tube bundle according to an embodiment of theinvention.

FIG. 8A is a representation of a prior art counterflow directevaporative cooling tower.

FIG. 8B is a representation of a counterflow indirect evaporativerefrigerant condenser/cooling tower according to an embodiment of theinvention.

FIG. 8C is a representation of different counterflow indirectevaporative refrigerant condenser/cooling tower according to anembodiment of the invention.

FIG. 9A is a representation of a prior art closed circuit cooler.

FIG. 9B is a representation of closed circuit cooler according to anembodiment of the invention.

FIG. 10A is a representation of a prior art induced draft evaporativecondenser/cooler.

FIG. 10B is a representation of an induced draft evaporativecondenser/cooler according to an embodiment of the invention.

FIG. 10C is a representation of another embodiment according to theinvention.

FIG. 10D is a representation of a further embodiment according to theinvention.

FIG. 10E is a representation of yet another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a cross-section of a condenser tube according to anembodiment of the invention. As shown in FIG. 1, the tubes of theinvention are formed in the shape of an extreme ellipse, with the majoraxis of the tube at least 3× the minor axis. According to preferredembodiments, the height of the tube (major axis) is at least 1.4 inches(outer diameter), and the width of the tube (minor axis) is no greaterthan 0.5 inches (outer diameter). A preferred embodiment is shown inFIG. 2, in which the ratio of the major axis to the minor axis is 6.4:1.According to further preferred embodiments, the minor axis may be 0.1inches to 0.25 inches, and the major axis may be 1.4 inches to 1.6inches with ratios of major axis to minor axis of 3:1 to 16:1.

Referring to FIGS. 3-6, the tubes of the invention may be arranged inrows of parallel single pass tubes, each tube running from an inletheader to an outlet header. The embodiment shown in FIGS. 3-6 showsmultiple inlet and outlet headers, with each row of tubes having its ownset of headers. According to an alternative embodiment, a single headermay be provided at each end of the bundle, with all tubes from all rowsterminating at one end at a single inlet header, and terminating at theother end at a single outlet header.

In either case, the lack of return bends as in the prior art serpentinetubes substantially reduces the height of the tube bundle for the samecapacity. Horizontal tube spacing is preferably 0.5 inches to 0.75inches, center to center. The spacing between adjacent tube sides ispreferably 0.25 to 0.65 inches. Vertical tube spacing is preferably 0.5inches to 2.0 inches, center to center.

FIG. 7B shows a closed circuit cooler/condenser in which the prior artserpentine coil has been replaced with an ultra-narrow elliptical tubebundle according to tn embodiment of the invention. Standard coolingtower nozzles distribute water over the ultra-narrow elliptical tubebundle of the invention, and the water collects in a basin at the bottomof the device from which it is pumped back to the nozzles. Ambient airis drawn into the plenum of the device at the bottom under the action ofa fan and is drawn up through the tube bundle to exit the device fromthe top.

FIG. 8B shows a counterflow indirect evaporative refrigerantcondenser/cooling tower according to an embodiment of the invention inwhich a refrigerant condensing tube bundle according to the inventionhas been placed into a standard counterflow direct evaporative coolingtower. As shown in FIG. 8B, the tube bundle can act as the structuralsupport for the fill, the sheets of which run perpendicular to thecondenser tubes. Standard cooling tower nozzles distribute water overthe fill, and the water collects in a basin at the bottom of the devicefrom which it is pumped back to the nozzles. Ambient air is drawn intothe plenum of the device at the bottom under the action of a fan and isdrawn up through the tube bundle and the fill to exit the device fromthe top. According to the embodiment shown in FIG. 8B, the tubes runparallel to the longitudinal axis of the tower. FIG. 8C shows anembodiment in which the tubes run perpendicular to the longitudinal axisof the tower.

FIG. 9B shows the tube bundle of the invention in an open cooling towerembodiment having a closed circuit water-to-fluid heat exchanger below.As shown in FIG. 9B, the tube bundle is located at the bottom of thedevice, and air is drawn into a plenum of the device through sideopenings located above the tube bundle. Air is drawn through the filland forced out through the top of the device. Spray nozzles from a waterdistribution system spray water over the fill. The water is collected ina tray and then redistributed over the tube bundle, cooling the fluidtherein via indirect heat exchange. The water collects in a basin at thebottom of the devices and is then pumped back to the spray nozzles.Since no air is directed over the tubes, the tube spacing can be muchtighter, and the tube bundle of the present invention allows for muchtighter spacing with the extreme elliptical shape and the lack of returnbends.

FIG. 10B shows a tube bundle according to the invention in an induceddraft evaporative condenser unit with crossflow fill. The tube bundle islocated directly beneath the spray nozzles of the water distributionsystem, and the fill is located below the tube bundle. Air enters thedevice through the sides at the bottom, adjacent the fill, as well asthrough the top above the tube bundle. Air flows downward through thetubes before exiting to the fan plenum. Water flows over the tube bundleand then over the fill to collect in the basin, from which it is pumpedback to the water distribution system.

According to further embodiments, the tube bundles of the invention maybe located above (FIG. 10C), below (FIG. 10D) and/or in the middle (FIG.10E) of the crossflow fill. According to these embodiments, only wateris directed over the tubes, and no air flow is directed over the tubes.

Having now fully set forth the preferred embodiments and certainmodifications of the concept underlying the present invention, variousother embodiments as well as certain variations and modifications of theembodiments herein shown and described will obviously occur to thoseskilled in the art upon becoming familiar with said underlying concept.It should be understood, therefore, that the invention may be practicedotherwise than as specifically set forth herein.

1. A tube bundle for an evaporative refrigerant condenser comprising arefrigerant inlet header, a refrigerant outlet heater, and a pluralityof straight single pass tubes extending between said refrigerant inletheader and said refrigerant outlet header, said tubes having across-sectional shape in the form of an ellipse having a major axis anda minor axis, wherein said major axis is longer than said minor axis bya factor of 3 to
 10. 2. The tube bundle according to claim 1 whereinsaid major axis has a length of 1.4 inches to 1.7 inches, outside tubediameter.
 3. The tube bundle according to claim 1, wherein said minoraxis has a width of 0.1 inches to 0.25 inches, outside tube diameter. 4.The tube bundle according to claim 1, wherein said major axis has alength of 1.4 inches to 1.7 inches, outside tube diameter and whereinsaid minor axis has a width of 0.1 inches to 0.25 inches, outside tubediameter.
 5. The tube bundle according to claim 1, wherein each tube isspaced from each horizontally adjacent tube by 0.5 inches to 0.75inches, center to center.
 6. The tube bundle according to claim, whereineach tube is spaced from each vertically adjacent tube by x inches to yinches, center to center.
 7. An evaporative refrigerant condenser orclosed circuit fluid cooler comprising: a housing; a fan located near atop of said housing to draw air into said housing and force it throughsaid top of said housing; a water distribution system, including a pumpand water distribution nozzles, said water distribution nozzles locatedbeneath said fan; a tube bundle located beneath said fan, said tubebundle comprising a refrigerant inlet header, a refrigerant outletheater, and a plurality of straight single pass tubes extending betweensaid refrigerant inlet header and said refrigerant outlet header, saidtubes having a cross-sectional shape in the form of an ellipse having amajor axis and a minor axis, wherein said major axis is longer than saidminor axis by a factor of 3 to 10; a plenum located beneath said tubebundle, a water basin located at a bottom of said plenum for collectingwater distributed from said water distribution system; said pumpconfigured to draw water from said water basin and force it through saidwater distribution nozzles; an air inlet on at least one side of saidhousing adjacent said plenum to allow entry of air drawn by said fan. 8.The evaporative refrigerant condenser or closed circuit fluid cooleraccording to claim 7, further comprising a direct heat exchange filllocated between said water distribution nozzles for facilitating directheat exchange between said air and said water.
 9. The evaporativerefrigerant condenser or closed circuit fluid cooler according to claim7, wherein said direct heat exchange fill rests directly on said tubebundle, and said tube bundle provides structural support for said directheat exchange fill.
 10. A counterflow closed circuit cooler orrefrigerant condenser comprising: a housing; a fan located near a top ofsaid housing to draw air into said housing and force it through said topof said housing; a water distribution system, including a pump and waterdistribution nozzles, said water distribution nozzles located beneathsaid fan; a direct heat exchange fill located beneath said waterdistribution nozzles for facilitating direct heat exchange between saidair and said water; a plenum located beneath said direct heat exchangefill, a redistribution basin located beneath said plenum and configuredto collect water distributed from said water distribution nozzles andredistributed it to a lower portion of said housing; a tube bundlelocated beneath said redistribution basin, said tube bundle comprising arefrigerant inlet header, a refrigerant outlet heater, and a pluralityof straight single pass tubes extending between said refrigerant inletheader and said refrigerant outlet header, said tubes having across-sectional shape in the form of an ellipse having a major axis anda minor axis, wherein said major axis is longer than said minor axis bya factor of 3 to 10; a water basin located at a bottom of said housingfor collecting water distributed from said water distribution system;said pump configured to draw water from said water basin and force itthrough said water distribution nozzles; an air inlet on a side of saidhousing adjacent said plenum to allow entry of air drawn by said fan.11. An induced draft evaporative condenser or closed circuit coolercomprising: a housing; a fan located near a top of said housing to drawair into said housing and force it through said top of said housing; awater distribution system, including a pump and water distributionnozzles, said water distribution nozzles located adjacent said fan; atube bundle located beneath said water distribution nozzles, said tubebundle comprising a refrigerant inlet header, a refrigerant outletheater, and a plurality of straight single pass tubes extending betweensaid refrigerant inlet header and said refrigerant outlet header, saidtubes having a cross-sectional shape in the form of an ellipse having amajor axis and a minor axis, wherein said major axis is longer than saidminor axis by a factor of 3 to 10; a direct heat exchange fill locatedbeneath said tube bundle for facilitating direct heat exchange betweensaid air and said water; a plenum located beneath said fan, a waterbasin located at a bottom of said housing for collecting waterdistributed from said water distribution system; said pump configured todraw water from said water basin and force it through said waterdistribution nozzles; an air inlet on a bottom side of said housingadjacent said fill to allow entry of air drawn by said fan.